LM5146: 2-phase Buck converter simulation doesn't look as expected.

Abhishek Deouskar

Part Number: LM5146
Other Parts Discussed in Thread: LM5145-Q1, LV5144, , LM5145, LM5149-Q1EVM-400, LM5149-Q1, LM5148-Q1, LM5149, LM5148

Tool/software:

Hello,

I am trying to develop a 13.5V, 40A buck converter. For the same, I decided to go with LM5146 in a 2-phase configuration with each phase carrying 20A.

Initially I tested with 1-phase and things are operating as expected. But with the 2-phase design, the things seem to get a bit wonky with the Output Voltage and Current.

I have added all my material at this link: Buck_Converter. I am hoping for some expert advice on this.

PS: My input voltage range is 30V to around 95V. I am also looking to develop this design to be pin swappable with LV5144, LM5146-Q1, LM5145, LM5145-Q1 based on different Vin(max) requirements.

5 months ago

0 Taru Kapoor 5 months ago

TI__Genius 11645 points

Hi Abhishek,

Can you share the schematic with me? Please also fill in the quick start design calculator for this device (for each phase) - and share with me: https://www.ti.com/tool/LM5145DESIGN-CALC

More comments:

LM5146 is a voltage mode control which is not the best suited topology for using in a dual phase operation. Since voltage mode control does not use inductor current information in the control loop, so accurate current sharing between the two phases is more difficult to ensure.

However, you can refer to this app note: https://www.ti.com/document-viewer/lit/html/SSZT900 (based on LM5145)

You can use LM5149-Q1 or LM5148-Q1 which are capable of dual-phase designs. Also LM5149-Q1EVM-400 is available and does 48V to 12V / 8A for single phase. You can potentially tie two EVMs together and reconfigure them for dual-phase. However, the abs max voltage for these devices is 85V.

Thanks,

Best Regards,

Taru

0 Abhishek Deouskar 5 months ago in reply to Taru Kapoor

Prodigy 20 points

Hello Taru,

The schematic and the quick start calculator are added here: Buck Converter

Meanwhile I will explore the LM5148 and LM5149 for the dual phase as well as incorporate design recommendations from App note.

Thanks,

Abhishek

0 Taru Kapoor 5 months ago in reply to Abhishek Deouskar

TI__Genius 11645 points

Thanks Abhishek!

I'll go through the design you have shared and get back to you.

You can look at these reference designs: https://www.ti.com/tool/PMP23420; https://www.ti.com/tool/PMP23392 (GaN based Design).

Thanks,

Best Regards,

Taru

0 Abhishek Deouskar 5 months ago in reply to Taru Kapoor

Prodigy 20 points

Hi Taru, Was following up on this. Do you have any recommendations?

0 Taru Kapoor 4 months ago in reply to Abhishek Deouskar

TI__Genius 11645 points

Hi ABhishek,

Sincere apologies for the delay.

Reviewing the files that you have shared with me. I have a few requests/ comments:

1. Please share the simulation file that you are using. I didn't see that in the folder that you have shared.

2. Are you doing load transients on the output?

3. Since your design is 540W - this maybe challenging to achieve considering you may be thermally limited by the FETs. With the current configuration also - there is around 6W of power dissipation in the top FET. You may want to look at the reference designs that I had shared.

Thanks,

Best Regards,

Taru

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LM5146: 2-phase Buck converter simulation doesn't look as expected.